sendButton.MouseButton1Click:connect(function()
print'clicked'
NewM(script.Parent.Parent.Parent.Parent, messageBox.Text)
messageBox.Text = 'Message'
end)
"clicked" is never printed, NewM is a valid function, and the message box's text is not changed. I haven't scripted in a while so I'm not sure about the MouseButton1Click event or anything.

2 comments
Ah. I think I was using the click detector event.
Well, actually, the 'MouseButton1Click' event is on the WIKI, and is a real event. :P And, Golden, 'MouseClick' is the event for a 'Click Detector' type instance, 'MouseButton1Click' fires when you click on a GUI type instance [TextButton, ImageButton].